The monoether 2-methallyloxyphenol (MOP) is useful as an intermediate in the synthesis of benzofuranyl insecticides as disclosed in U.S. Pat. No. 3,474,170. As also described in the patent, MOP is commonly produced by the reaction of methallyl chloride (MAC) with catechol (also known as "pyrocatechol"). However, significant amounts of undesired diether, 1,2-dimethallyloxybenzene, are also obtained. Furthermore, secondary (ring) alkylation reactions also occur, characterized by direct substitution of the methallyl radical onto the aromatic nucleus to form 3-methallylcatechol and/or 4-methallylcatechol. The formation of diether and 4-alkylated derivatives reduces the yield of the desired monoether (MOP) and results in a mixture of compounds from which it is difficult and expensive to isolate the monoether.
Formation of undesirable amounts of by-products is commonly controlled by the use of a large excess of catechol and by limiting catechol conversion. However, this process is inefficient and uneconomical because it requires recovery and recycling of large proportions of the catechol charge, typically about 50%. In another process, described in U.S. Pat. No. 4,252,985, methallyl chloride is reacted with catechol in the presence of a basic agent and a catalyst, using a stirred, two-phase liquid reaction medium comprising water and a water-immiscible, inert organic solvent. The catalyst is a quaternary ammonium or phosphonium derivative. The preferred organic solvent is anisole, although methallyl chloride can act as both the reactant and the water-immiscible solvent. Despite the benefit of selective mono-etherification, the reaction is complicated by the aqueous phase because unreacted catechol collects therein as well as in the anisole phase and must be extracted for later recovery and recycling. Moreover, some of the catechol remains in the product MOP, thereby requiring further purification.